1. Field of the Invention
The present invention relates generally to systems and methods for providing assessment of a subject with disorders such as disequilibrium, balance or motion disorders and, more particularly, to a system and method for providing assessment by measuring a subject's performance of predetermined tasks and comparing said performance with expected parameters associated with said tasks.
2. Background of the Invention
Balance, or a state of equilibrium, may be described as the ability to maintain the body's position over its base of support. In particular, the optimal posture for controlling balance typically requires maintaining the body's center of gravity (COG) within the base of support, such as the support frames defined by the foot soles. Balance may be divided into static balance and dynamic balance, depending on whether the base of support is stationary or moving. Dynamic balance, even during voluntary movements, is particularly complex task for humans; stability depends on the kinetics, motor control, sensory information, neuro processing delays and environmental conditions. Ambulation such as exemplified with walking gait, requires anticipatory, reflex and voluntary control of a multi-dimensional biomechanical system, yet is a task that healthy adult humans do with ease.
Disequilibrium and movement and balance disorders can be debilitating and increase the potential for falls. A movement disorder is a condition that prevents normal movement. Some movement disorders are characterized by lack of controlled movement, and while others are characterized by excessive movement. A balance control disorder is typically the result of sensory and/or motor disorders which impair equilibrium control by a subject. Balance control disorders may be bilateral, i.e., affect a subject on both left and right sides, or may only be manifested on one side. Movement and balance disorders may be caused by disorders in the vestibular, somatosensory, or central or peripheral nervous systems.
The vestibular system carries sensory information related to body equilibrium, specifically roll, pitch, and yaw motion oriented relative to the direction of gravity. Information is generated by the semicircular canals and maculae in the inner ear, relayed by the vestibular nerve to the brainstem vestibular nuclei, and processed by the vestibular nuclei and mid brain with corresponding muscular contraction and relaxation known as motor output.
Aspects of the somatosensory system include: 1) perception of pressure, vibration, and texture, i.e., discriminative touch, 2) perception of pain and temperature, and 3) proprioceptive sensation. Proprioception, which is often referred to more generally as the somatosensory system, involves awareness of movement derived from muscular, tendon, and joint articular surfaces provided by the peripheral nervous system and processed in the parietal lobe of the brain. These interoception senses provide internal feedback on the status of the body, indicating whether the body is moving with required effort and indicating where various parts of the body are located in relation to each other. Thus, proprioception involves the essential stimuli provided to, or received by, skin, joints, and/or muscles to maintain equilibrium or balance control.
Damage to any part of the central or peripheral nervous systems may interfere with balance control. Central nervous system processing includes the brain primary motor cortex responsible for generating the neural network impulses controlling execution of movement, the posterior parietal cortex responsible for transforming visual information into motor commands, the premotor cortex responsible for sensory guidance of movement and control of proximal and trunk muscles of the body, and the supplementary motor area responsible for planning and coordination of complex movements such as coordinated activity using limbs.
In particular, vision plays a significant role in balance. Indeed, up to twenty percent of the nerve fibers from the eyes interact with the vestibular system. A variety of visual dysfunctions can cause disequilibrium. These dysfunctions may be caused directly by problems in the eyes, or may be caused indirectly by disorders related to stroke, head injury, vestibular dysfunction, deconditioning, decompensation, or the like.
Meanwhile, the peripheral nervous system generally relates to the conduction of sensory information, or messages, from the peripheral nerves to the brain and spinal cord. For example, such sensory information may indicate that there is a pressure on the sole of a foot or that a toe is flexed. Sensory information may also indicate that the feet are cold or that a finger is burned.
Accordingly, the body relies on the interaction of several systems to control movement, balance, and posture. For example, the vestibular system in the ears orient upright stance, especially when the eyes are closed. The cutaneous, proprioceptive sensory system feels pressure under the feet. In addition, the joint and muscle spindles are sensitive to joint position and movement. Moreover, cognition or brain processing estimates the motor response magnitude. In sum, balance disorders are predominantly multi-causal with imbalance occurring due to deficits in more than one sensory, motor, neuro or cortical pathway.
Traumatic brain injury (TBI) or mild traumatic brain injury (mTBI), occurs when physical trauma causes temporary or permanent neurological damage. mTBI typically involves temporary impairment of neurological function which usually quickly resolves by itself, and conventional neuroimaging normally shows no gross structural changes to the brain as the result of the condition. Overt symptoms may often include balance (M. Scherer and M Schubert, Traumatic Brain Injury and Vestibular Pathology as a Comorbidity After Blast Exposure, PHYS THER. Vol. 89, No. 9, September 2009, pp. 980-992) and spatial disorientation problems (vertigo) related to vestibular dysfunction, vision disturbances, inner-ear edema, and/or other sensory integration deficits. Treatment of this particular population group has several challenges which include: early and specific injury assessment, the determination of appropriate return-to-duty measures and selection of effective individualized balance rehabilitation and treatment tools. The group is also highly variable in the nature and extent of balance deficits and cognitive and/or related psychological impairments but it appears that almost all subjects show some susceptibility to vestibular or vestibular/ocular disorders.
The cause and extent of any deficits in a subject's movement and balance control may, in prior art, be determined by assessing the subject's ability to control movement and balance while performing a number of standard functional motor tasks, such as standing still, moving from a sitting position to a standing position, walking, walking on steps and uneven surfaces, or the like. This assessment may also be achieved by manipulating sensory input and monitoring motor response. Quantified sensory assessment, for example, may examine touch-pressure, two-point discrimination, inner ear response to warm and cold, or visual acuity by reading the print on an eye chart. Diagnosis may also be determined qualitatively according to the observations by an examining physician or a physical therapist.
There is a clear need for objective measurements both to assess the patient's original deficit and their rate of progress through rehabilitation. Therefore data capture and analysis, even while completing therapeutic activities (for example during functional movement tasks) can be used to provide information to the therapist, optimize motional limit tasks and adaptively alter feedback settings and motional task difficulty. In particular, certain functional gait tasks are known in prior art to be reliable and accurate indicators of behavior functional ability. However, previous efforts to measure performance during functional gait tasks rely on human observations and subjective scoring.
The system and method of the invention is useful for achieving objective assessment of patient deficit, and is also useful for providing therapeutic training. As further described below, the use of three dimensional cameras to measure variance and rate of change of variance is a particularly novel aspect of the system and method of the present invention. Furthermore, the combining of multi-sensor signals which include both inertial and three dimensional camera measurements, or, in yet a further embodiment of the system and method of the invention the combining of inertial, three dimensional camera, and force plate measurements, to quantify variance and rate of change of variance is also a particularly novel aspect of the invention. There are other aspects of the invention as described herein that are novel and non-obvious relative to the prior art.
After a balance deficit has been assessed and quantified using the system and method of the invention, a physician may prescribe remedial measures to try and bring the subject's balance control near or within normal limits. In certain instances, the physician may prescribe medication that reduces the action of peripheral senses on the brain or enhance neural network function. Alternatively, the physician may prescribe a course of physical therapy, which will typically last at least several months, with the object of training the subject's brain to deal with a reduced sense of balance when trying to maintain the body upright and prevent a fall. Normally, neither of these techniques will have an immediate effect on the subject's balance deficit. Moreover, medication can have side effects, and can also reduce the capability of the brain to process balance information from the peripheral senses. A traditional course of physical therapy requires a long training period which may extend over more than two months. These difficulties and limitations associated with conventional remedial measures for dealing with balance deficits are most problematic when the subject has suffered a blast related head injury, or is older and likely to have a falling tendency.